Free Molecule Micro-resistojet: Nanosatellite Propulsion

Constellations and platoons of small satellites can offer an assortment of benefits over larger, single function spacecraft. The strict mass, volume, and power limitations of small satellites will require unique micro-technologies to help develop efficient propulsion systems for maneuvering. The Free Molecule Micro-Resistojet (FMMR) has been analyzed and tested in this study to determine its applicability for an upcoming Texas A&M (TAM) nanosatellite mission. The nanosatellite mission will demonstrate the performance and survivability of a water propelled FMMR for attitude control maneuvers and could mark the first meaningful operation of a Microelectromechanical Systems (MEMS) fabricated thruster in space. The Mark 3.1 design of the FMMR heater chip uses a deposited serpentine heater pattern to resistively heat a gaseous propellant expanding through long (13 mm), narrow (100 μm) slots. Experimental data shows that the FMMR, with a heated wall temperature of 575 K, can attain a specific impulse of 65 seconds with a thrust level of 1.2 mN for a nitrogen gas propellant with a mass flow of 100 SCCM. The expected specific impulse when run on a water vapor propellant is expected to be 80 sec at similar thrust levels. Higher thrust levels can be achieved by increasing the temperature of the FMMR heater chip and / or the propellant mass flow through the expansion slots. The measured performance of the FMMR in this study has proven to be adequate to perform the attitude control maneuver for the TAM nanosatellite.